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Solar Energy to Biomass - Optimisation of light energy conversion in plants and microalgae

Periodic Reporting for period 1 - SE2B (Solar Energy to Biomass - Optimisation of light energy conversion in plants and microalgae)

Reporting period: 2016-03-01 to 2018-02-28

In the face of the increasing global consumption of fossil resources, photosynthetic organisms offer an attractive alternative that could meet our rising future needs as clean, renewable, sources of energy and for the production of fine chemicals. Key to the efficient exploitation of these organisms is to optimise the conversion of Solar Energy into Biomass (SE2B). The SE2B network deals with this optimisation in an interdisciplinary approach including molecular biology, biochemistry, biophysics and biotechnology. Regulation processes at the level of the photosynthetic membranes, integrating molecular processes within individual proteins up to flexible re-arrangements of the membranes, will be analysed as a dynamic network of interacting regulations. SE2B will yield information about the similarities and differences between cyanobacteria, green algae, diatoms and higher plants, the organisms most commonly employed in biotechnological approaches exploiting photosynthetic organisms, as well as in agriculture.
The knowledge gained will be directly transferred to increase the productivity of algal mass cultures for valuable products, and for the development of sophisticated analytic devices used to optimise this production. In future, the knowledge created can also be applicable to the design of synthetic cell factories with efficient light harvesting and energy conversion systems.
WP1: The objectives are to elucidate the role and function of specific thylakoid proteins, LHCs, PsbS and LhcSR, and certain carotenoids involved in the regulation of light use efficiency. This will help to understand the evolution of regulation mechanisms from algae to land plants, and allows for the exploitation of the effect of xanthophyll over-accumulation on photosynthesis for biomass production in algae. Mutants containing only PSBS, LHCSR1 or LHCSR2 have been obtained and will be analysed by ultrafast spectroscopy. Progress has been made to investigate the changes in energy fluxes during NPQ in LHCII and PS II-LHCII complexes. The experiments to describe the role of certain proteins in quenching mechanisms in evergreens are promising. The investigation of systems for non-invasive monitoring of plant fitness and growth performance is delayed, because of recruiting problems. To use algal mutants for enhanced carotenoid production first attempts to identify the down-stream biosynthesis enzymes are underway.
WP2: The main objective is to study the formation, molecular structure and dynamics of supercomplexes in the thylakoid membrane and to disclose the physiological significance of such dynamics for the performance of the organism under varying environmental conditions. The factors involved in supercomplex assembly, i.e. phosphorylation and lipid composition, as well as functional changes like NPQ or ST, will be determined in plants, green algae, diatoms and cyanobacteria, thereby integrating results obtained on single proteins in WP1, and on whole organisms in WP3. The study on changes in supercomplex formation related to functional changes (NPQ and ST) has shed light on the energy landscape and excitation energy transfer dynamics of CP29 pigments and their role in photo-protection. The individual protein composition of thylakoid pigment protein complexes has been resolved and analysed and a manually annotated gene library for spruce thylakoid proteins has been created. In diatoms PSII supercomplexes are purified (WP2, MS5) and the protein composition of those will be studied by mass spectrometry. Homologous of OCP C-terminal-domain (CTDH) were characterized and their interaction with OCP N-terminal-domain homologues (HCP) was studied. OCP mutants were constructed in E. coli and are being characterized. Knock-out ApcD and ApcF mutants were characterized in self-constructed S. elongatus mutants. The structural studies of photosynthetic supercomplexes, namely Photosystem II and Photosystem I, isolated from different organisms are in line with proposed plan.
WP3: The objectives are to elucidate the role of the thylakoid membrane flexibility in light use efficiency in vivo, by characterising the functional and structural (re)organization of thylakoid membranes during NPQ and ST in cyanobacteria, green algae, and diatoms, to determine the extent to which NPQ and ST make use of the same underlying physical mechanisms in different organisms. The development of protocols/models for the quantitative assessment of photosynthesis in different types of microorganisms will be used to improve productivity in cultures of microalgae. The arrangement of the thylakoids in C. reinhardtii and chloroplasts isolated from the spinach were imaged and differences according to the PSI/PSII emission properties were detected. Progress has been made on the construction of mutants of Synechococcus sp PCC 7942. Also the change in excitation energy distribution between PSI and PSII during state transitions (ST) in the cyanobacteria S. sp. PCC 6803 and S. elongatus (MS10) has been studied. The works in the stress of the culture conditions of Nostoc Sp. has been partially solved despite some delays, because the strain was received late. The quantification of photosynthesis in intact photosynthetic algae and cyanobacteria is delayed because of problems to find an appropriate ESR.
WP4, 5, 6 and 7: SE2B aimed to recruit 15 ESRs that are highly qualified and
In three cases progress far beyond the state of the art has been made: i) Novel biochemical tools to investigate the composition of thylakoid protein complexes in evergreen conifers have been developed and are utilized to investigate the individual protein composition of thylakoid pigment protein complexes of Norway spruce. Resolving the winter acclimation strategies and educating people understanding these mechanisms is also very important to be able to design sustainable forestation.
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